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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 889 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

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  1. 1.In triangle ABC, angle A = 24° and angle B = 22°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 80° and 72°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 21° and angle B = 118°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 93° and angle B = 34°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  6. 6.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 11 cm, 10 cm and 7 cm? (a) Yes (b) No
  8. 8.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  16. 16.Can a triangle have sides of 3 cm, 2 cm and 6 cm? (a) No (b) Yes
  17. 17.In triangle ABC, angle A = 62° and angle B = 43°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 80° and 67°. What is the exterior angle (in degrees)?
  19. 19.In triangle ABC, angle A = 92° and angle B = 29°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 2 cm, 12 cm and 11 cm? (a) Yes (b) No
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 79° and angle B = 72°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 97° and angle B = 61°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 32° and 61°. What is the exterior angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  32. 32.Can a triangle have sides of 8 cm, 4 cm and 2 cm? (a) No (b) Yes
  33. 33.The two interior opposite angles of a triangle are 29° and 72°. What is the exterior angle (in degrees)?
  34. 34.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 40° and angle B = 42°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 31° and 76°. What is the exterior angle (in degrees)?
  37. 37.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  38. 38.Can a triangle have sides of 9 cm, 19 cm and 7 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?

Answer key

  1. 134
  2. 152
  3. 41
  4. 53
  5. 102
  6. 40
  7. Yes
  8. 36
  9. 90
  10. 77
  11. 23
  12. 75
  13. 45
  14. 26
  15. 7
  16. No
  17. 75
  18. 147
  19. 59
  20. 11
  21. 56
  22. 71
  23. Yes
  24. 30
  25. 29
  26. 58
  27. 64
  28. 44
  29. 22
  30. 93
  31. 90
  32. No
  33. 101
  34. 25
  35. 98
  36. 107
  37. 5
  38. No
  39. 45
  40. 126

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